Make logs human-readable

Description

I have activate the Logs function but is very difficult
to understand WHO download WHAT and if the download of
a file was finished correctly.
I think that would be one good option to have the
posibility of a specific log for the operations of
download/upload, something like: ID, Account, IP,
Operation, TransferFile, Time, response.

Operation: Download or Upload
Response: Ok or Interrupted

Practically the reassumed of what happens in the bottom
of server interface.

I don't like Microsoft IIS for some reasons, but their logs are quite enough for non-debugging purposes.
They are nearly human readable, except FTP success codes, which are used instead of words.
I need to store all logs, and FileZilla logs take too much disk space.
And they are difficult to understand as rightly mentioned by Fabio Maulo, particularly because of their huge size.
Please, make some options regarding style of logging.
One of the possible examles is Microsoft IIS FTP service truly customizable logging.